Lumbar puncture

 

A guide to indications / contraindications / procedural technique related to performing a lumbar puncture

 

Lumbar puncture is a potentially uncomfortable procedure that must not be rushed. It is essential to position the patient correctly and take your time.

 

Indications

  • Diagnosis
    • Evaluate CSF in suspected meningitis, SAH, carcinomatosis, multiple sclerosis and syndromes such as Guillain-Barré.
    • Measure CSF pressure.
      • Therapeutic
    • Intrathecal administration of medications.
    • Removal of CSF in benign intracranial hypertension.

 

Contraindications

  • Increased ICP
  • Space occupying lesion
    • Intracranial masses, particularly in the posterior fossa, may cause brain herniation and compress the brain stem.
  • Uncontrolled bleeding diathesis
    • Patients with coagulopathy, those taking anticoagulant medications or with a platelet count <40 x 109/L are at increased risk of epidural haematoma.
  • Local skin infection.

 

Indications for a CT head scan prior to lumbar puncture

  • Age >60 years
  • Immunocompromised state
  • Neurological findings, such as ALOC or focal neurological deficits
  • Objective evidence of raised ICP such as papilloedema, bradycardia and headache
  • History of CNS lesion (e.g. stroke, mass lesion, focal CNS infection)
  • Seizure activity in the preceding week

 

Equipment

  • Sterile gloves
  • Dressing pack
  • Local anaesthetic (10 mL of 2% lignocaine)
  • 10 mL syringe
  • Needles (21G and 25G)
  • Spinal needles (20G (black), 18G (yellow))
  • Skin cleaning solution (e.g. chlorhexidine)
  • Gauze swabs
  • Manometer with 3-way tap
  • Three sterile collection bottles (check with laboratory before commencing procedure to confirm correct specimens to be collected)
  • Assistant to reassure patient and to assist with CSF collection
  • Sticking plaster
  • Absorbent pad or ‘bluey’

 

Procedural technique

  • Identify the correct patient. Explain the procedure and gain verbal consent. If the patient is anxious or unable to tolerate lying still for 15–30 minutes, sedate with 2–5 mg PO or IV diazepam prior to the procedure.
  • Position the patient correctly (Fig 59.1)
    • Lay the patient on the left hand side on the bed with the back as close to the right edge of the bed as possible.
    • Place one hand on the patient’s right shoulder and one on the right anterior superior iliac spine and ask the patient to maximally flex the hips, knees and neck (fetal position).
    • Ensure the back is straight, the vertebral column parallel to the edge of the bed and the shoulders square to the hips.
    • Palpate the iliac crests and locate the vertebrae lying on an imaginary line between them (L4 vertebrae).
    • Feel the space above the vertebrae (L3–4 space) and the space above that (L2–3 space). Mark with a pen cap.
  • Wash hands and put on sterile gloves
  • Ensure you are in a comfortable position, seated by the side of the bed with the patient’s spine at the level of your sternum.
  • Use sterile technique to prepare and drape the site.
  • Anaesthetise the skin using the 25G needle and SC infiltration. Use the 21G needle for deeper infiltration to the interspinous ligament. Wait 2–3 minutes for full effect of local anaesthetic.
  • Check the stylet moves freely within the LP needle and check the manometer taps.
  • Locate the L3 and L4 vertebrae with the index and middle fingers of the non-dominant hand, and use these as physical landmarks. The anaesthetised area should be in the midline directly between these fingers.
  • Place the LP needle, bevel up and at 90 degrees to the skin in all planes, or 5–10 degrees caudad (i.e. needle tip pointing up to the head) over the potential space ( 59.2).
  • Advance the needle through the skin, between the spinous processes, aiming cranially towards the patient’s umbilicus.
  • Feel the increased resistance (interspinous ligament) and then a ‘give’ as the needle passes through the ligamentum flavum.
  • Withdraw the stylet look for ‘flashback’ of CSF. If there is none, replace the stylet and advance the needle another few millimetres, checking for evidence of CSF return each time.
  • Once the subarachnoid space has been reached, and clear CSF is draining, remove the stylet fully and attach the manometer.
  • Measure the CSF pressure (normal opening pressure is 6–18 cm H2O).
  • Disconnect the manometer and collect CSF drops from the open end of the spinal needle. Collect 5–10 drops into three specimen containers and label 1, 2, and 3. Send to laboratory for cell count with differential, xanthochromia, Gram stain and culture (bacteriology and cytology). Depending on the pathology service requirements, a further tube with preservative may be required to analyse biochemistry and glucose.
  • Re-insert the stylet and slowly remove the entire spinal needle.
  • Clean the patient’s back and place a small dressing or plaster over the puncture site.
  • Move the patient slowly into a prone position if possible (back uppermost) to reduce CSF leak by gravity. Recommend bed-rest for 1–2 hours (depending on local hospital policy), although it does not influence the likelihood of post-LP headache.

 

Complications

  • Ask a senior doctor for help.
  • Post-LP headache—more likely with larger bore needle, multiple attempts, excessive CSF removal, dehydration, women
  • Brainstem compression secondary to brain herniation
  • Local haemorrhage
  • Epidural haematoma
  • Infection: epidural abscess, meningitis
  • Infection

 

Handy Hints

  • If you cannot get into the epidural space
    • Make sure the patient is correctly positioned.
    • Ensure the needle enters the skin at 90 degrees to the skin in all planes in the midline between two vertebrae.
    • If you feel you are in the right space, slowly rotate the needle through 90–180 degrees to release the needle bevel.
  • If you still cannot drain CSF
    • Give yourself and the patient a short break. Ask for help.
    • Reposition the patient in a sitting position, with legs hanging over the edge of the bed and head and shoulders flexed forwards over a table. Re-determine landmarks and repeat procedure.
  • Do not remove too much CSF, only 5–10 drops are required per specimen container. Excessive removal leads to an increased risk of post-LP headache.
  • NEVER apply suction to the spinal needle.

 
 

Date implemented – 05/2009
Revision date – currently being revised
Author – Mike Cadogan

 
 

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